h1{
    height: 100px;
    width: 400px;
    line-height: 100px;
    border: 1px solid peru;
}

/* span{
    width: 400px;
    height:100px;
    padding:10px;
    margin: 10px;
    border: 1px solid #ffccdd;
}

a{
    display: block;
    width: 100px;
    height: 100px;
    line-height: 100px;
} */

a{
    display: inline-block;
    width: 200px;
    height: 100px;
    border: 1px solid #00c;
}
a:hover{
    background-color: #00c;
    
}

div.box_before{
    width: 350px;
    height:30px;
    background-color:green;
}

div.box{
    width: 350px;
    height: 150px;
    margin:25px;
    padding: 25px;
    border: 5px solid black;
}

div.box_after{
    width: 350px;
    height:30px;
    background-color:green;
}

div.box_outline{
    width:500px;
    height:300px;
    border: 2px solid blue;
}

div.box_size{
    width: 50%;
    height:auto;
    margin:0 auto;
    max-height: 100px;
    background-color: crimson;
}

div.box_margin{
    width: 300px;
    height:100px;
    /* margin:20px;
    margin-top:50px;
    margin-left:50px; */
    margin:0 auto;/*水平居中*/

    background-color: #00c;
}
div.box_margin2{
    width: 300px;
    height:100px;
    /* margin:20px;
    margin-top:50px;
    margin-left:50px; */
    /* margin:0 auto;水平居中 */

    background-color: red;
}

div.box_outline p{
    width:100px;
    height:30px;
    margin-left: 30px;
    padding: 5px 0 0 5px;
    border:1px solid black;
}